I had a triple helix antenna several years ago and a preamp certaininly helped that and all other antennas that I used. You need to get the noise figure below 1 dB on 70 cm and the relationship is non-linear when pointing the antanna away from earth -- going from 6 dB to 1 dB improves the signal to noise ratio by up to 10 dB. The noise figure of a receiving system without a preamp is the noise figure of the receiver plus the feedline loss so preamps are most effective if they are mounted at the antenna.
73,
John KD6OZH
----- Original Message ----- From: "Andrew Rich" [email protected] To: "Amsat-Bb@Amsat. Org" [email protected] Sent: Monday, December 10, 2007 09:14 UTC Subject: [amsat-bb] Helix and pre-amp
I am keen to hear from others that may have added a pre-amp to a helix.
Does it help ?
I have made a 9 turn on 70cm - thinking of going to 16 turns.
Andrew Rich VK4TEC [email protected] http://www.tech-software.net
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